Researchers analyzed medical and school records for 8,548 children in Olmsted County, about 70 miles southeast of the Twin Cities. They cautioned that findings might vary in an area with very different demographics, but said the study is important for eventually answering the question of whether ADHD is being over-diagnosed and overmedicated.

`Potential overdiagnosis of the disorder and overuse of stimulant medications make it imperative to obtain accurate information about the occurrence of ADHD,” said the study, published in the March issue of the Archives of Pediatrics and Adolescent Medicine.

ADHD is the most common neurobehavioral disorder in childhood. Symptoms may include short attention span, impulsive behavior, and difficulty focusing and sitting still. Symptoms must occur in two settings, such as home and school, for an accurate diagnosis.

Previous studies estimated that ADHD affects anywhere between 1 percent and 20 percent of school-age children. The American Academy of Pediatrics says it affects between 4 percent and 12 percent of school-age children – or as many as 3.8 million youngsters.

The Mayo Clinic study of children born from 1976-1982 also reviewed records of youngsters treated at the area’s only private psychiatric practice.